Ahem, my AI is calling bullshit... In the U.S., almost all beef cattle eat grass and/or hay for a big part of their lives (cow–calf and often “stocker/backgrounding” phases). The split you’re asking about is really how they’re finished right before slaughter: Best “apples-to-apples” split: grass-finished vs grain-finished Grain-finished (corn/other concentrates; may include soy, wheat, byproducts): ~95% of U.S. cattle are finished on grain for roughly the last 160–180 days (on average). (extension.psu.edu) Grass-finished (forage-only finishing): ~5% by implication of the same estimate. (extension.psu.edu) That “grain-finished” bucket is where corn is dominant and rations often include additional energy/protein sources (which can include soybean meal, wheat, distillers grains, etc.; soy is common but not universal). What you’ll see in typical supermarkets (retail availability metric) Some research summarized by the beef industry indicates that ~99% of beef in major retail supermarkets is from conventionally raised, grain-fed/grain-finished cattle. (beefresearch.org) That’s a retail-channel statistic (not total production), but it matches most shoppers’ experience. Market-share view (sales, not production) An extension summary estimates grass-fed beef is ~4% of U.S. beef retail + foodservice sales, with ~1% labeled/marketed as grass-fed and the rest effectively blending into conventional channels. (extension.sdstate.edu) Why the percent can look different depending on the definition USDA slaughter “by class” data illustrate that most slaughter is steers + heifers (fed cattle), with a smaller share cows + bulls (often older “cull” animals whose diets are more forage-based, though they can still receive supplements). For example, May 2024 federally inspected slaughter was 49.8% steers + 31.6% heifers = 81.4%, vs 17.0% cows + 1.6% bulls = 18.6%. (marketwatch.com) So depending on whether you mean “finished diet”, “what’s sold as grass-fed”, or “what’s in supermarkets”, you’ll see numbers like ~95/5, ~96/4, or ~99/1.